During the berry harvesting season, large numbers of blueberries, gooseberries, raspberries and cherries need to be quickly destemmed before they are packaged for shipment. Machines have been developed for destemming such fruit, such as the machine disclosed in Pertics U.S. Pat. No. 3,680,618. The disclosed machine employs an endless fruit conveying belt made of a plurality of metal support rods covered with plastic tubing Each metal rod also has a piece of rubber tubing for contact with a stationary member which causes the roller to rotate. The rubber tubes are offset on the same ends of adjacent rollers and the stationary members are positioned above and below the rods so that adjacent rollers roll toward each other, forming a nip for gripping the stem and pulling it off of the berry.
The machine such as disclosed in the above-mentioned patent performed well for the intended purpose. However, it did suffer from several drawbacks. For example, the smooth plastic surface on each roller tended to cause the fruit to stick to the surface of the roller which resulted in heavy fruit damage due to skinning. The continuous fruit conveyor belt was also supported on spaced sprockets and, if a piece of stone or debris came between the chain and one of the sprockets, the chain would have to travel further and, in turn, would jump time causing all of the rollers to then cant. In order to put the machine back in alignment, the machine would have to be stopped and the strain taken off the chain so that it could be moved forward or backward into alignment. Since the machines are being used at the peak of the berry picking season, workers would be required to wait for the machine to be put back into alignment before resuming activities in feeding berries to the machine and packaging the product leaving the machine Another problem presented was that as the berry growing season progresses, the fruit becomes larger and softer. In the Pertics machine, the fruit was subjected to a continual destemming operation from one end of the machine to the other which resulted in loss of fruit due to skinning of the soft, overripe fruit The rollers in the machine also presented problems in that the plastic tubing was easily damaged by debris and was also easily stained and difficult to clean In the movement of the conveyor belt, the rotation of the rollers was dependent on frictional engagement between the aforementioned rubber tubing and a stationary member in the machine. Since a frictional contact was required, the movement would often be erratic as the rubber frictional member contacted dry and wet surfaces on the stationary member. The erratic movement of the rollers also resulted in fruit damage and loss of destemming action.